In the prior art, aluminum alloys such as AA3003, AA3104, AA3107 and AA5052 are extensively used as general and specific purpose sheet products. Exemplary uses for these types of alloys include semi-rigid container stock for poultry roasting pans, frozen dinner trays or the like. Cutter bars typically used in connection with consumer wrap containers are also formed using these types of aluminum alloys.
AA3003 is a preferred alloy for these types of applications because it combines corrosion resistance, strength and formability. However, when using this type of alloy in thin gauge applications such as semi-rigid container stock or general purpose sheet, e.g. 0.035 inches up to 0.125 inches, the alloy must be homogenized between cold rolling steps to achieve the requisite properties at final gauge.
With reference to FIG. 1, a known AA3003 aluminum alloy can be cast by conventional techniques and cold rolled to an intermediate gauge.
Following the cold rolling step to intermediate gauge, the rolled aluminum alloy is subjected to a high temperature thermal or homogenization treatment to principally achieve the proper grain size in the final gauge product. Without this homogenization treatment, the final product will have a non-uniform grain size which adversely effects the mechanical properties and makes the final gauge sheet product unacceptable for commercial use.
Following the cold rolling of the AA3003 to final gauge, a known temper practice such as H19, H24 or 0 temper can be employed to achieve the desired mechanical properties. The treated sheet product can then be fabricated, slit or otherwise formed or shipped for its intended use.
The homogenization treatment between the cold rolling steps described above is typically conducted at high temperatures due to the high manganese content of these types of aluminum alloys. These high temperature homogenization or thermal treatments drastically increase plant operating costs due to fuel consumption in the furnaces. This intermediate anneal also increases handling and manpower costs associated with the sheet product and ultimately increases the final product unit cost.
In view of the disadvantages above, a need has developed to provide an alternative aluminum alloy composition and method of sheet processing which provide acceptable levels of strength and elongation in the final gauge product while reducing energy consumption and operating and unit costs.
In response to this need, the present invention provides both an aluminum alloy composition and method of processing which eliminate the intermediate thermal treatment required with prior art aluminum alloys. The method produces a sheet product having acceptable mechanical properties for use in applications such as semi-rigid container stock, fin stock, general purpose aluminum alloy sheet and consumer wrap cutter bars.